The present invention relates to pulse generators, and in particular to an electrical contact-free pulse generator, which uses a Hall effect device to provide an output pulse relative to shaft position.
Electrical pulse generators are frequently used for electromechanical control systems to initiate or terminate a mechanical function. Frequently a rotating shaft must be synchronized with the control mechanism in order to perform the function at a prescribed time of a particular cycle. Mechanical position sensors, which sense the position of a rotating shaft are subject to fatigue since the moving parts wear out with constant use. Static sensing devices which utilize light beams and photoelectric sensors have not been entirely satisfactory in areas where the atmosphere is lint laden, since the lint and dust in the area cause the sensors to become obscured, thereby reducing the sensitivity and accuracy of the sensors and requiring frequent maintenance.
Other known position sensing devices, used on a rotating shaft for synchronization thereof, include a permanent magnet affixed or coupled to a rotating shaft cooperating with an electromagnet sensor, which provides an electrical pulse each time the permanent magnet passes over a gap provided in the electromagnet's core. Other pulse generators known in the art, utilize a rotating magnet and a stationary Hall effect device to sense and provide a pulse each time the permanent magnet becomes proximate the Hall device. Still other sensing devices which operate in conjunction with a rotating shaft utilize an electromagnet which has a core provided with an air gap. A non-flux conducting disc, provided with openings therein, is generally affixed or coupled to the shaft and placed in the air gap of the electromagnet. When the non-flux conducting portion of the disc is within the air gap of the electromagnet the flux lines are broken and the inductance of the electromagnet decreases. When the disc rotates so that the opening of the disc is within the air gap of the electromagnet the inductance of the electromagnet increases. This change of state of the electromagnet may be used directly or indirectly, e.g. to control the feedback of an oscillator, thereby, yielding an output which is related to the position of the shaft. In addition, known in the prior art is a spirally shaped permanent magnet, which is affixed to a shaft proximate a Hall device. Rotating the shaft changes the output or state of the Hall device in varying amounts relative to the position of the shaft upon which the magnet is affixed. Generally, the prior art devices require that the permanent magnet device be affixed to the rotating shaft, or the flux lines of the magnet be cut to effect a change in the state of the sensors. All of the pulse generators of which we are aware provide a signal responsive to the shaft positions of a rotating member, however, none of the prior art systems, to our knowledge, utilize a stationary permanent magnet and a stationary Hall effect device, proximate thereto, to provide signal pulses responsive to the discrete positions of a rotating member.